The industry is constantly seeking to improve the processes used to manufacture integrated circuits from wafers. The improvements come in various forms but, generally, have one or more objectives as the desired goal. The objectives of many of these improved processes include: 1) decreasing the amount of time required to process a wafer to form the desired integrated circuits; 2) increasing the yield of usable integrated circuits per wafer by, for example, decreasing the likelihood of contamination of the wafer during processing; 3) reducing the number of steps required to turn a wafer into the desired integrated circuits; and 4) reducing the cost of processing the wafers into the desired integrated circuit by, for example, reducing the costs associated with the chemicals required for the processing.
One of the most crucial processes in the fabrication of integrated circuits involves the rinsing and drying of the semiconductor wafers between various chemical processing steps. During rinsing, DI water is often used to assist in the removal of chemicals from the surface of the wafer. After rinsing is completed, the wafer surface must be dried. It is during the drying step that wafer contamination often results. Such contamination is due to the fact that the evaporation of the DI water deposits contaminant particles on the wafer surface.
Various techniques have been proposed for the rinsing and drying of semiconductor wafers. One technique used to both rinse and dry wafers relies upon a spin rinser/dryer. Such a system uses a DI rinse water spray to rinse the wafer. The wafer is spun during the drying step thereby removing the water from the surface of the semiconductor wafer through evaporation and the action of centripetal acceleration.
Other techniques used to dry wafers include the use of IPA vapor dryers, full displacement IPA dryers, and other forms of IPA dryers. These IPA dryers rely upon a large quantity of a solvent, such as IPA and other volatile organic liquids, to facilitate drying of the semiconductor wafer. One limitation of this type of dryer is its use of large solvent quantities which are highly flammable and often hazardous to health and environment. Further, these dryer types are often quite expensive. Still further, the large quantities of hot solvent are often incompatible with certain recessed pattern wafers and may be detrimental to certain device structures.
Another drying technique uses hot DI process water to rinse and promote drying of the semiconductor wafer. Since the DI water is heated, the liquid on the wafer evaporates faster and more efficiently than DI water at standard ambient temperatures.
A still further drying technique is known as a Marangoni dryer. In a Marangoni dryer, the wafer is slowly withdrawn from the rinsing liquid in an atmosphere having a vapor that is miscible with the rinsing liquid. As the wafer is withdrawn, a meniscus is formed at the wafer surfaces. The surface tension of the rinsing fluid at the meniscus is reduced as a result of the presence of the vapor. The reduced surface tension gives rise to a substantially particle free drying process.
In each of the foregoing processes, one or more wafers are disposed in an open chamber during the rinsing and/or drying process. In the open chamber, the semiconductor wafers are exposed to a large rinse bath and relatively large area of ambient air. Particles that contaminate the wafer during the rinsing and drying processes often come directly from the rinse water and ambient air. Control of the contaminants in the rinsing bath and ambient air in these systems is often difficult and requires rather elaborate filter systems.
The inventors have has recognized that demands for integrated circuit rinsing/drying processes may ultimately require more control and economic efficiency from the rinser/dryer. As such, a substantially new approach to rinsing and drying of the semiconductor wafer has been undertaken which provides greater control of the physical properties of the rinsing and drying fluids. Further, wafers may be rinsed and dried on an individual basis more quickly when compared to the drying of an individual wafer using any of the foregoing processes.